Was the Sumas Flood caused by global warming? Proof says no.

news7g11/22/2021

6 4 minutes read

Was the Sumas Flood caused by global warming? Proof says no.

Last weekend, flooding caused extensive damage in Northwest Washington, with the town of Sumas and surrounding areas inundated with floodwaters. Several landslides have occurred, including several closures of I5 near Bellingham.

Sumas Town, 2021, WSDOT . Photo

Within hours of this heavy downpour, politicians and the media assumed the event was somehow unique and the result of global warming.

For example, Governor Inslee called the flooding an example of “a condition that is frequently hit by the forces of climate change.” The New York Times attributes the flooding in Northwest Washington to climate change (see below)

The truth is very different from these claims. The Sumas area is very prone to flooding and has been flooded many times before. And as I will show below, there is no evidence that global warming causes the heavy rainfall associated with this event.

Flooded area

The town of Sumas lies within the historic floodplain of the Fraser River, with additional flood risk from local rivers such as the Nooksack (see map below from a 2005 report by Dr. Jacek Scibek and Dr. Diana Allen of Simon Fraser University)

Importantly, there is a large historic lake near Sumas and Abbotsford (Lake Sumas) that has been drained for agricultural use. In short, a historically wet, low-lying area is always at risk of flooding.
The previous flood
Flooding is not a new visitor to the Sumas area, which has experienced numerous floods over the past century. Streets in Sumas were similarly flooded in February 2020 (see below)

And there have been many major floods before that, including those in 1990 and 1951, to name a few just a few (see some more examples from ) Whatcom particle analysis of floods). You build a town in the historic river delta in one of the wettest regions of North America, you could be in trouble.

To say that flooding in Sumas or the region is something new, unprecedented or unique is simply not true. Those making such claims should take a moment to consider the area’s historic floods..
Global warming and heavy rainfall
There were many people talking about the heavy rainfall during this event, claiming it was the result of global warming. Or it has been greatly enhanced by global warming.
Yes, we had a heavy rain event, but to confirm that global warming is the source, need to demonstrate that heavy rainfall is increasing, something that could be indicative of the source of global warming.
Let’s look at the data. Karin Bumbaco, Washington State Deputy Climatologist, graciously provided me with charts of 24-hour annual maximum precipitation in Bellingham, WA, and at nearby official climate observation site Clearbrook, with the latter having a very long record (see below).
NO HINT of a more extreme rainfall trend at either of these locations. According to Karin, the large peak in the mid-1930s was caused by an error in bringing two days of rainfall into one day.

The lack of evidence for such global warming is consistent with modern regional climate models, which suggest that climate models (driven by very strong increases in greenhouse gas emissions) RCP8.5) did not produce a significant increase in the maximum 24-hour period of precipitation in the region over the past half-century (results for Bellingham shown below).At the end of the century (not shown). here), positive global warming will increase the heaviest precipitation…but that is in the future.

But wait! There is even more evidence against the contribution of global warming to this localized heavy rain event.
The source of this event was a river with a temperate atmosphere in which a narrow amount of water vapor was forced up by local mountains (see steam chart at 4pm last Sunday).

If global warming were important, one would look for above-normal sea surface temperatures along the atmospheric river path, which would add extra moisture to the air.
Below are sea surface temperature anomalies (differences from normal) for the previous time period and including the atmospheric river in question. It was cooler than usual immediately off our coast and is nearly normal for almost the entire atmospheric river path. With La Nina conditions, water temperatures near the equator BELOW normal. There is no indication of the contribution of global warming.

Wildfires don’t contribute to flooding
In desperation, some global warming advocates are suggesting, without a shred of evidence, that the wildfires from last summer contributed to the flooding. Specifically, they argue that debris from fires and the poorer absorption capacity of burned landscapes has led to more water and material entering the river.
We were able to see how much of the land immediately around the flood areas had burned using NASA’s MODIS imagery (see below for October 31, when it’s clear). Recently burned landscapes are red (I showed an example of a recent fire, east of the Cascade Peak, with a red arrow.

It is clear that no major fire areas around the flood area or related watersheds received heavy rainfall during this event. So the forest fire areas do not cause these fires.
Snowpack
Another claim, as found in the New York Times, is that there was a low snow cover (due to global warming) prior to the flood, resulting in a reduced infiltration of rainwater. But that’s not true: the snow cover was higher than normal before the event (USDA Snotel map a few days before the flood is shown below). The snow cover is higher than normal… .. not exactly the kind of situation related to global warming. I mean MUCH above normal.

The end
It is worrisome and problematic that some local politicians, the local and national media, and even some scientists are willing to give the truth about the origin of the flood event. This severity shows a large contribution from global warming (often referred to as “climate change”).
Society cannot effectively deal with environmental threats when it is fed with exaggerated or false information. And providing such misinformation, even in the hope of motivating people to “do the right thing,” has significant ethical issues.

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news7g11/22/2021

6 4 minutes read